The present invention relates generally to a hybrid-type electric vehicle. More particularly, the invention relates to an electric rotary machine for driving the hybrid drive type vehicle and generating an electric power, and a control method therefor. Further particularly, the invention relates to an electric rotary machine, in which a rotor of the electric rotary machine is constructed with a first field magnet and a second field magnet, and which is variable of effective flex amount depending upon a direction of torque.
As a conventional hybrid drive type vehicle, there are (1) a series hybrid type driving a generator by an output torque of an engine as an internal combustion engine for obtaining an electric power and driving a electric rotary machine connected to a wheel axle by the electric power for driving a vehicle by a driving torque generated by the electric rotary machine, and (2) a parallel hybrid type, in which a part of the output torque of the engine is converted into an electric power and remaining output torque is transmitted to the wheel axle as driving torque for driving the vehicle by a driving torque of the electric rotary machine using the generated electric power and the wheel axle driving torque of the engine.
In the recent trend, in view point of sizes and costs for the motor and/or battery, attention is attracted to (2) the parallel hybrid driving type vehicle. For example, as disclosed in Japanese Patent Application Laid-Open No. 9-132042 (1997), a parallel hybrid drive type vehicle of the type wherein the engine and two electric rotary machines are connected to respective shafts of a planetary gear mechanism and a driving force is distributed depending upon load and revolution speed of the engine and respective electric rotary machines (this type will be hereinafter referred to as xe2x80x9ctwo motor systemxe2x80x9d), has already marketed.
However, such prior art requires two electric rotary machines and two inverter circuits for driving the electric rotary machines and newly arranging the planetary gear mechanism and thus requires significant reconstruction of the vehicle to cause significant increase of the cost associating therewith.
Therefore, as shown in Japanese Patent Application Laid-Open No. 7-298696 (1995), there has been proposed a system, in which an electric rotary machine is directly connected to a crankshaft of the engine for switching driving mode and generating mode in one electric rotary machine (this system will be referred to as xe2x80x9csingle motor systemxe2x80x9d). This single electric rotary machine system is advantageous in view point of cost and capability of add-on the existing vehicle.
In both of single motor system and two motor system, as the electric rotary machine, a permanent magnet field type electric rotary machine arranged a permanent magnet on a rotor or a squirrel cage induction electric rotary machine, in which a secondary conductors made of aluminum alloy or copper alloy are arranged on the rotor in cage-like fashion, may be employed.
As set forth above, the single motor system is more advantageous than the two motor systems in viewpoint of the cost. However, the following constraints are present even in the single motor system.
(1) It has to be achieved both of a high torque characteristics in low revolution speed range upon starting-up of the engine and high-power generation characteristics in high revolution speed range.
(2) A revolution speed to generate a torque (maximum torque to be generated by the motor) upon starting-up of the engine is less than or equal to one tenth for a motor revolution speed at the allowable maximum revolution speed of the engine.
(3) The present invention is directed to the electric rotary machine mounted on the vehicle, and as a power source, a battery charging and discharging within a voltage variation range centered at a certain voltage, is employed. Therefore, if a voltage far beyond a charging voltage of the battery is charged, it is possible to damage the battery in the worst case.
The present invention has been worked out in view of the shortcoming in the prior art as set forth above. It is therefore an object to provide a hybrid drive type vehicle having a permanent magnet type synchronous motor obtainable of high torque characteristics in low revolution speed range of the engine and high power generation characteristics at high revolution speed range of the engine.
According to one aspect of the present invention, a hybrid drive type vehicle comprises:
an internal combustion engine driving a vehicle;
a battery charging and discharging an electric power;
an electric rotary machine mechanically connected with a crankshaft of the internal combustion engine for starting up the internal combustion engine as driven by the electric power supplied from the battery, and driven by revolution of the internal combustion engine for performing generation for charging the battery;
an inverter for controlling driving and generating of the electric rotary machine;
a controller controlling the inverter;
revolution speed detecting means for detecting a revolution speed of the internal combustion engine or the electric rotary machine;
the electric rotary machine being formed with a stator having a primary winding and a rotor having a field magnet, the field magnet being constituted of a first field magnet alternately arranged mutually opposite magnetic poles in sequentially in circumferential direction and a second field magnet capable of causing relative angular displacement relative to the first field magnet and alternately arranged mutually opposite magnetic poles in sequentially in circumferential direction, the first and second field magnets being opposing with a magnetic pole of the stator and having a mechanism for varying a phase of a magnetic pole resulting from combination of the first and second field magnets relative to the magnetic pole of the first field magnet depending upon direction of a torque of the rotor,
the mechanism for varying the magnetic pole depending upon the direction of the torque including means for aligning centers of the same magnetic poles of the first and second field magnets by balance between torque direction generated in the rotor and magnetic action between the first and second magnetic and means for causing offset of the center of the same magnet poles of the first and second field magnetic associating with generation of the torque generated in the rotor in the opposite direction.
Operation of one aspect of the invention as set forth above will be discussed.
In FIG. 6, the characteristics of an effective flux relative to a rotational angular velocity of the permanent magnet type synchronous electric rotary machine, an induced electromotive force, and a terminal voltage are shown.
An induced electromotive force E0 of the permanent magnet type synchronous electric rotary machine is determined by a constant magnetic flux "PHgr" generated by the permanent magnet and rotational angular velocity xcfx89 of the electric rotary machine. Namely, as shown in FIG. 6, when the rotational angular velocity xcfx89 of the electric rotary machine (revolution speed) is increased, the induced electromotive force E0 of the electric rotary machine is proportionally increased. However, as an essential condition in mounting on the vehicle is charging of the battery. In order to charge the battery, the induced electromotive force to be generated in the electric rotary machine has to be suppressed to be lower than or equal to a battery charge voltage so as not to damage the battery. Therefore, in the permanent magnet type synchronous electric rotary machine, it requires to perform weakening field control for reducing magnetic flux generated by the permanent magnet in range of the revolution speed higher than or equal to a predetermined value.
Since the induced electromotive force is increased in proportion to the rotational angular velocity, current for weakening field control has to be increased. Therefore, a large current has to flow through the coil as the primary winding to inherently cause heating of the coil. Therefore, efficiency of the electric rotary machine is lowered in the high revolution speed range to possibly cause demagnetization or so forth of the permanent magnet due to heating beyond cooling capacity.
Therefore, according to one aspect of the present invention, the first field magnet and the second field magnet of the rotor of the electric rotary machine are arranged coaxially for varying the centers of the magnetic poles of the first and second field magnets depending upon the direction of the rotational torque so that the centers of the same magnetic poles of the first and second field magnets are aligned upon serving as an electric motor in the low revolution speed range, such as upon starting up of the engine or the like to provide large effective flux amount by the permanent magnet opposing to the magnetic poles of the stator to attain high torque. Next, upon serving as the generator, when the rotating direction of the rotor is the same, the torque to be applied to the rotor becomes opposite to that applied upon serving as the electric motor to cause offset of the centers of the same magnetic poles of the first and second field magnets to reduce effective flux amount by the permanent magnet opposing the magnetic poles of the stator to attain weakening field effect to obtain high power generation characteristics in high revolution speed range.
In the preferred construction, the electric rotary machine serves as an electric motor at low revolution speed range and having means for aligning centers of the same magnetic poles of the first and second field magnets by balance between torque direction generated in the rotor and magnetic action between the first and second magnetic, and serves as a generator at high revolution speed range and having means for causing offset of the center of the same magnet poles of the first and second field magnetic associating with generation of the torque generated in the rotor in the opposite direction. Also, the electric rotary machine serves as an electric motor at low revolution speed range and having means for aligning the first and second field magnets at an initial position by balance between torque direction generated in the rotor and magnetic action between the first and second magnetic, and serves as a generator at high revolution speed range and having means for causing offset of the center of the same magnet poles of the first and second field magnetic associating with generation of the torque generated in the rotor in the opposite direction, and the mechanism for varying the center of the magnetic pole associating with variation of the torque direction is constructed by rigidly securing the first magnet on a shaft and separating the second field magnet from the shaft, and the shaft and the second field magnet are permitted to cause relative angular offset within an angular range corresponding to circumferential length of one magnetic pole for causing offset of the center of the poles of the first field magnet and the center of the poles of the second field magnet. A stopper may be provided at a position away from the side surface of the second field magnet. A serve mechanism may be provided for displacing the stopper in parallel to the shaft depending upon revolution speed.
According to another aspect of the present invention, an electric rotary machine comprises:
a stator having a primary winding and a rotor having a field magnet, the field magnet being constituted of a first field magnet alternately arranged mutually opposite magnetic poles in sequentially in circumferential direction and a second field magnet capable of causing relative angular displacement relative to the first field magnet and alternately arranged mutually opposite magnetic poles in sequentially in circumferential direction, the first and second field magnets being opposing with a magnetic pole of the stator and having a mechanism for varying a phase of a magnetic pole resulting from combination of the first and second field magnets relative to the magnetic pole of the first field magnet depending upon direction of a torque of the rotor,
the mechanism for varying the magnetic pole depending upon the direction of the torque including means for aligning centers of the same magnetic poles of the first and second field magnets by balance between torque direction generated in the rotor and magnetic action between the first and second magnetic and means for causing offset of the center of the same magnet poles of the first and second field magnetic associating with generation of the torque generated in the rotor in the opposite direction.
The mechanism for varying the center of the magnetic pole associating with variation of the torque direction may be constructed by rigidly securing the first magnet on a shaft and separating the second field magnet from the shaft, and the shaft is formed with a threaded portion serving as a bolt and an inner periphery of the second field magnet being formed with a thread for serving as a nut for connection in thread engagement, and a stopper is provided at a position away from the side surface of the second field magnet, and a serve mechanism for displacing the stopper in parallel to the shaft depending upon revolution speed.